The sulphurous cliffs were dyed in many a brilliant shade of brown and orange by the admixture of various ores, but their brightness seemed strange and unnatural, and the dizzying whirls of vapor, now enveloping the whole scene in gloom, now lifting in this spot and now in that, seemed to magnify the dismal pit to an indefinite size.  Now and then there would come up from the very entrails of the mountain a sort of convulsed sob of hollow sound, and the earth would quiver beneath his feet, and fragments from the surrounding rocks would scale off and fall with crashing reverberations into the depth beneath; at such moments it would seem as if the very mountain were about to crush in and bear him down in its ruins.

Father Francesco, though blinded by the smoke and choked by the vapor, could not be content without descending into the abyss and exploring the very penetralia of its mysteries.  Steadying his way by means of a cord which he fastened to a firm projecting rock, he began slowly and painfully clambering downward.  The wind was sweeping across the chasm from behind, bearing the noxious vapors away from him, or he must inevitably have been stifled.  It took him some little time, however, to effect his descent; but at length he found himself fairly landed on the dark floor of the gloomy inclosure.

The ropy, pitch-black undulations of lava yawned here and there in red-hot cracks and seams, making it appear to be only a crust over some fathomless depth of molten fire, whose moanings and boilings could be heard below.  These dark congealed billows creaked and bent as the monk stepped upon them, and burned his feet through his coarse sandals; yet he stumbled on.  Now and then his foot would crush in, where the lava had hardened in a thinner crust, and he would draw it suddenly back from the lurid red-hot metal beneath.  The staff on which he rested was constantly kindling into a light blaze as it slipped into some heated hollow, and he was fain to beat out the fire upon the cooler surface.  Still he went on half-stifled by the hot and pungent vapor, but drawn by that painful, unnatural curiosity which possesses one in a nightmare dream.  The great cone in the centre was the point to which he wished to attain,—­the nearest point which man can gain to this eternal mystery of fire.  It was trembling with a perpetual vibration, a hollow, pulsating undertone of sound like the surging of the sea before a storm, and the lava that boiled over its sides rolled slowly down with a strange creaking; it seemed the condensed, intensified essence and expression of eternal fire, rising and still rising from some inexhaustible fountain of burning.